I think it is interesting to discuss the difference between the leavening role of the starter in bread vs. pizza. In the Neapolitan pizza oven, the heat is so intense, surely the yeast are dead before they have a chance to look for the emergency exit. In the much cooler bread oven, the yeast have plenty of time to prepare their wills, get their final affairs in order, and produce a nice bounce before they succumb after a few minutes.

So if this correct, then the yeast in the starter do their job during fermentation and proofing, producing pockets of gas throughout the dough so that, if the dough is properly handled and shaped, these pockets expand in response to the intense heat to produce the wonderfully light texture of the Neapolitan pizza.

Bill/SFNM

Great use of metaphor, Bill. I think you'd be correct that the gas is already present in the pizza dough to give it lift: hence the lesser rise of middle where the skin has been de-gassed by pressing down or stretching out, and the greater rise along the cornicione.

What confuses me about the yeast getting their affairs in order in the bread metaphor is this: are you positing that lower temps would have the yeast still actively producing gas as they begin to succumb to the temps, giving bread its greater rise? Because I would think that interior temperatures would rise fairly quickly, even at 400-450F ranges, and that the rise of bread would still be 99% due to pre-existent gases. You simply have a thicker starting dough that you've been careful in handling so that it doesn't come out a dense unrisen loaf.

Interesting stuff.

Logged

Education: that which reveals to the wise, and conceals from the stupid, the vast limits of their knowledge. --Mark Twain

What confuses me about the yeast getting their affairs in order in the bread metaphor is this: are you positing that lower temps would have the yeast still actively producing gas as they begin to succumb to the temps, giving bread its greater rise? Because I would think that interior temperatures would rise fairly quickly, even at 400-450F ranges, and that the rise of bread would still be 99% due to pre-existent gases. You simply have a thicker starting dough that you've been careful in handling so that it doesn't come out a dense unrisen loaf.

Interesting stuff.

It has always been my understanding (I could be wrong) that the yeast are still active for quite a while inside the bread and that they contribute greatly to the oven spring. A thermometer inserted into a baguette will show the internal temps remain for several minutes, at least, before becoming fatal (you can hear them screaming if you listen carefully and their little screams accompanied by "last-gasp" exhalations of CO2.). This is one reason for slashing the loaves and injecting steam into the oven so that the expansion is not restricted.

However, it's hard to believe that yeasts which die at temps much over body temp would act much differently between 550 and 850 degrees. It's all conjecture, of course; without actually looking at the yeasts in action we can't know their precise time of death. Or whether they felt pain, or joy.

Like some others here I have observed differences in the action of the dough depending upon the state of the starter at incorporation. Early on, I figured that mixing the dough at high Kraeusen was only natural. All the books said to do it. And it just seemed to make sense to me. However, I have found that as long as the starter is viable, and has been fairly active within a week or so at room temperature, the differences in the final product are small indeed. When we make dough we are in fact giving our starter culture a really big feeding. Certainly if you underpitch your yeast, you will require more time for fermentation to get going.

Like humans, the yeast seem happiest when active. But the activity is most effective, in my observation, when the rate is stepped up incrementally. Small feeding, larger feeding, larger feeding; all the while the yeast are reproducing. Ideally one would take a small amount of starter culture, and step it up bit by ever-lovin' bit until you had a big wad of dough that was both the correct consistency (correct hydration level) and active as a child's mind.

When using yeast for brewing or winemaking, it's easy to determine the proper pitching rate: you measure the specific gravity of the wort and that tells you how much food is available for the little yeasties; you want approximately one million cells per milliliter of wort per one degree Plato. I guess if a guy wanted to figure out, for the sake of figuring out, exactly how much food were available in a given sample of flour, then he could also determine the exact number of yeast cells necessary to properly inoculate his sample, based on known nutrition requirements of the yeast.

Just the same, two cups of 'fairly active starter' added to two pounds of flour along with salt and enough water to make a really really sticky dough works well for me.

Regarding the amount of time yeast have before their demise in the oven, here are some data I collected today while baking a rustic loaf in my conventional oven (475F - stone mode). [...] Total baking time: 20 minutes. Final temp 195F, Estimated increase in volume 200%

Although this has already been covered pretty well in the past (mainly by Jeff), it bears repeating that expanding gases (and water vapor) due to heat is the primary power behind "oven spring." This applies to bread and pizza. I would like add in this particular situation, that it's not the "cooler" oven that's keeping the yeast alive for more than just two or three minutes at that temperature, it's the mass and shape of the bread dough. We're talking about the difference between 1-2 cm in the thinest dimension for pizza dough (in addition to directly facing the heat), and 10-20 cm for bread. That's an order of magnitude in difference.

Bill, what was the mass, physical dimensions, hydration, amount of yeast, and amount of rise time at what temperature for the dough you used for collecting data? Was it a thermistor or thermocouple probe, and how far bellow the surface of the dough did you place it? Did you have to keep opening the door to take the reading, or did you leave the probe in the dough throughout the entire baking process?

Bill, what was the mass, physical dimensions, hydration, amount of yeast, and amount of rise time at what temperature for the dough you used for collecting data? Was it a thermistor or thermocouple probe, and how far bellow the surface of the dough did you place it? Did you have to keep opening the door to take the reading, or did you leave the probe in the dough throughout the entire baking process?

- red.november

November,

This particular loaf was an experiment in hydration - the temperature measurements were just an afterthought. In this case, the surface area/volume ratio was similar to a thickish pizza.

I tried to keep the probe in the center as best as I could which necessitated adjusting it when I opened the oven to spray water (You can see the track marks of the probe (well actually the cable of the probe) in the photo below.

Other than opening the door to apply steam, the door was not otherwise opened.

I would say that your steaming kept the temperature rise to a minimum. When I first saw your data, my initial reaction was that your yeast started playing a diminishing role in oven-spring at around 7 minutes. When I plotted your temperature data against your data adjusted for yeast productivity and vapor pressure, it was pretty clear that your yeast stopped being a major player at around 6 minutes 59 seconds. The red "X" marked on the attached graph indicates where the temperature rise changed from logarithmic to exponential just as the yeast would have started to exhaust.

The most telling evidence of gas and water vapor expansion playing the major role is the amount of water lost. Essentially 24.5% of the water evaporated from the dough. You can't have that much water leave that size of a cellular structure in just 20 minutes without a great deal of pressure. This is even more true for a pizza crust baked in less time.

In the graph: green = temperature (68-123 F), gray = yeast productivity, blue = vapor pressure. You'll notice that the vapor pressure curve begins to fit the temperature curve exactly when the yeast begin to decline in productivity. In the region between the green line and blue line, where the green line is on top, yeast played a contributing role since this is evidence of a thermal byproduct of yeast activity. Everything else is physics at work.

For those of you that use starters, what indicators do you use to determine when your starter is "optimum". Any other thoughts greatly appreciated.

Bill/SFNM

I come from mainly a bread baking background but have a lot of experience with sourdough.

I would refresh the starter a number of times before using it if it is coming from the fridge. Coming out of storage the starter really has feeble activity. You need robust activity and this will only come if you feed the starter a few times. In general a starter coming out of the fridge lacks nutrients and is inhibited by fermentation byproducts. Feeding relieves this inhibition (by dilution and some neutralization of acid by flour proteins) and brings in nutrients. If you double the volume through a few cycles of feeding every 8-12 hours you can bring it back into good shape or sooner depending on the starter and temperature. The doubling approach is a conservative approach and the benefit is that the acidity keeps selective pressure against non desireable organisms. Alternatively you can make a fairly aggressive dilution (say a teaspoon of starter in a cup of flour+water). This will need less doublings but is slightly risky in that you loose the mild selective pressure against adventitious organisms that the acid provides.

A starter degrades dough quality faster than common yeast and this is the reason why you want a very active starter in your dough - . This is because the acidity allows more proteolysis to occur and the gluten is attacked more aggressively than with a dough prepped with yeast alone. The organisms are also geared to live off the flour so the window of useability is smaller than with normal yeast. So if you begin with a moribund starter you cannot afford to let time rescue you because you dough will have degraded.

The criterion I use to judge if the starter is optimally active is to look for a thick layer of bubbles above the starter like what you see as the head on beer - only with larger bubbles.

Natural Leaven. I don't know if you ever use a starter that is kept at more of a dough like consistency, but if you did how would you know when it was ready to be incorporated into your dough recipe?

Does my "wait until it has just stopped rising" method sound good? It works for me, but I am always trying to find a better way to deal with my beloved little friends.

If you frequently refresh a stiff starter and it is actively doubling through these refreshments you can be well assured that the starter is probably in good condition for baking. There is a caveat however.

One thing you have to keep in mind is that a volume increase is largely a function of gassing (both by yeast and lactobacilli) but the lactobacilli will provide most of the flavor. These activities need not be synchronous so if you rely on a volume increase as a signal it actually may not fully reflect what the flavor will be like. For example, the Sourdough International "Russian" starter or "Carl's" sourdough starter have robust leavening and peak leavening activity very early but develop flavor a lot later when leavening activity is almost dead. Other starters are "slower" with flavor and leavening somewhat synchronized. My feeling is this is largely controlled by the lactobacilli population - weak acid producers will not exert much inhibitory effect on the yeast and so leavening activity is robust early. Strong acid producers, exert an inhibitory effect sooner. So first you have to know how your culture behaves with respect to leavening and flavor and you have to use your judgment as to where your culture is on this spectrum and how and why you are using it - for leavening, for flavor or both.

In Pizza making as seems to be done on this board IDY or fresh yeast is also being used so the starter is largely for flavor and its gassing role will be supplemented by the yeast added. In this context it has to be realized that acidity gradually inhibits yeast activity ( even sourdough yeast, together with acceleration of decay of the gluten net alluded to before). So the timing issue is optimizing flavor within a window of good gassing & gluten integrity that you need to determine empirically for your starter and method (hydration, temps etc. will affect the speed of all these reactions).

For people with very hot ovens and stones, the strong push of direct bottom high heat will overcome a number of gassing limitations but if the gluten has degraded then texture will be compromised because it simply will not have the strength to hold gas leaving the liquid phase on exposure to high heat.

Lastly, in terms of time people should realize that even with a small inoculum the process is exponential and so dough quality can degrade quite fast. For example if you put 5% starter and assume a 6-8 hour doubling time for an active starter then in 6-8 hours you are at the equivalent of having added 10% in 12-16 hours 20% etc. Of course temperature and activity of the starter etc. influence this but I just want to draw attention to the fact that a small inoculum becomes a large fraction of the dough very quickly and so the time window of optimum activity & dough quality can run away from you quite fast.

One of the reasons I adopted a room-temp environment for my cultures is because of the lag between refrigeration and working temp. Since the cultures seemed to be happiest at room temp, I began leaving them there all the time. Also, observation of their habits is easier (for me anyhow). The dough (I make bread and pizza) develops excellent structure and flavors within a half day or so of fermentation and that's where I like to capture it...while the thing is really active. If I wait and bake the dough much after high kraeusen, both structure and flavors suffer greatly.

It's my impression that yeast activity during the primary phases of fermentation develops the gluten and therefore is primarily responsible for structure (and flavors) within the dough and that moisture escaping as steam is much more responsible for oven spring. Concur?

I agree that the cell movement in the dough caused by the fermentation process aids gluten development, although not as much as the kneading itself. Gas and water vapor expansion is definitely the primary cause of oven spring.

Optimum activity is important. Out of the fridge it takes several feedings and washings before it is no longer half-dormant. If you try to use it straight out of the fridge you'll have very poor results.

I also see the pattern post-feeding of a lag time of ~4 hours followed by a burst of bubbly activity of ~4 hours and then a decline of ~4 hours into a flat, quiescent state. I try to incorporate mine into the dough just at the peak of activity, just before the end of the burst phase at ~7 hours post-feeding.

Of course hydration and temperature affects all this. I am doing this at a room temp of ~75F and at a hydration level of 100%. This hydration is particularly useful because at this thickness the mixture will trap the gas as bubbles and thus expand up the container. That way, the max height of the mixture in the container correlates to the end of the burst phase where the yeast have run out of food. By using the same amount of starter and flour at the beginning, this spot is predictable so you can catch the yeast at the peak of its activity just before that point is reached.

I've noticed I can _really_ get the starter active if I do a wash and feed at this optimal point of activity once or even twice in succession, never letting the starter get into the decline phase. At that point it is convinced it is SuperStarter and just goes crazy - all the above times shorten.

I have a couple of starters that I work with..one is over 50 years old..

Saying that....I know people who keep and feed a starter all the time...they never keep it in the fridge.....

I on the other hand am a little lazy...Their are times when my starters will sit in the fridge for a couple of months, neglected and waiting for food..

I can pull them out..let them get to room temp. Add water and white flour...I just eyeball the amounts probably 48% water and 52% flour. I use to weigh it but found out that I get close enough. Once I see some action I will split the amount, half goes in the fridge and the other goes into a clean jar. I add more flour and water mixture and do this until I have to feed the beast every 4 hours.

This usually takes about 12 hours total. Sometimes more sometimes less..

Now I am not like most that keep a cup of starter in the fridge. I keep maybe a couple of tablespoons in the fridge. So when I have done my 12 hours to get an very active starter..I end up with a cup or so...

I am not a scientist and never played one on TV but when I make pizza I use different amounts of starter depending on when I need the dough. I sometimes only dip a spoon into the starter and work that into the dough..

If I want a dough with a real twang..I use my milk starter..and a very little amount and I keep it in the fridge for several days..

I have a couple of friends who make pizza and they are very scientific about how they make their dough. Sometimes their dough just doesn't work like they plan...

There is a lot of science in making pizza but there is a little art also. Throw in a starter and things can change.

I'm going to chime in here just because there's a very important part of the activation process that was left out of Ed's book and the instructions that come with the dry cultures. I've had The Book "Classic Sourdoughs" By Ed Wood for almost 2 years now and have bought many dry cultures from him. Never had a infection or any really long lag times before getting activation. That said I'm also a home brewer and use alot of dry yeast for beer, wine, and mead so I'm schooled about proper re hydration of dry yeast. Here's the problem i see that so many of you get contamination during the initial activation. The directions say to store dry cultures in the fridge until ready to activate, no problem there, but if you are taking the dry cultures out of the fridge and adding it cold and directly to the warm water and flour mixture then that's a huge problem. When re hydrating dry yeast it very important to let them come up to room temp before re hydrating adding the yeast to warm water. For home brew i take a pack of dry yeast out of the fridge and let it warm up for 1/2-1 hr before adding it to the 102-104 degree water per the direction on the pack of yeast. If you were to add the yeast straight out of the fridge in to the warm water it would kill a great deal of the yeast, and the remaining ones that are still viable are shocked and it will create a huge lag time in active fermentation, which opens the door for a infection. The same would apply to the dry sourdough cultures because they are yeast too. I just activated my Ischia culture last week and after 20 hrs had nice foam on top with no infection, but i followed my home brewing technique of letting the dry sourdough culture come up to 85 degrees before adding it to the warm water flour mixture. Hope this might help someone avoid the huge lag time and a infection with their sourdough cultures. Bryan

i take a pack of dry yeast out of the fridge and let it warm up for 1/2-1 hr before adding it to the 102-104 degree water per the direction on the pack of yeast. If you were to add the yeast straight out of the fridge in to the warm water it would kill a great deal of the yeast, and the remaining ones that are still viable are shocked and it will create a huge lag time in active fermentation, Bryan

KEWL! I recently switched from IDY to ADY (soon to a starter) but it has taken me about 5-6 dough batches to begin to figure out that the ADY worked better if it was allowed to warm before it's tepid bath.

I have been using my starter every couple of days, so what I've been doing (and correct me if this is wrong) is using it, then feeding, and sticking it right back in the fridge.

So when I take it out of the fridge, I don't need to feed it. I take it out around 7am, and by early afternoon it has doubled and is very bubbly/smells a little alcoholic but not sour. I use some, feed it and put it back.

Another q I had was when the starter bulks up, should you stir it before measuring... or does it not really matter? I guess if you are doing it by weight (as opposed to volume) it doesn't matter? I do not have a scale yet.

I use my starters straight from the fridge. After mixing and short hand kneading i leave them out overnight at room tem, to encourage the yeast to grow. The next day i judge how much it has risen, if it is quite active then it goes into the fridge until i am ready to use it. I take it out an hour or to before use for it to come up to temperature, however i find slightly cold dough easier to handle and form. If it is very slow to rise i leave it at room temp, or even mix a little more starter in.

This works pretty well for me. Maybe it is not optimum. I think it may depend on the starter also. I have used the re-activating the starter by feeding and leaving at room temp, but i think maybe laziness inclines me not to bother, and i am gettign good rises on my pies.

Just took a starter out of the fridge yesterday that had been dormant for at least seven months.I have washed it twice and fed it.All appears to be well.I've another couple in there also that I plan on leaving longer to see if any problems arise?

Logged

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I just weighed out 140 g flour and 140 g water and the mixture is quite thick. Almost chunky. Is this how it should be or did I measure incorrectly (sometimes I do something dumb like put pressure on the scale while pushing "tare").